PCM (Pulse Code Modulation) signal compression is a basically known operation for reduction of the number of bits of the words of the signal, prior to its transfer to a transmission line.
The logic circuits already known in the technique to carry out PCM compression are basically of the combinatory type.
If such combinatory-logic circuits were to be integrated as part of LSI integrated circuits, they ought to be implemented, according to the already known techniques, either by conveniently programmed read-only memories, or by PLA logic networks (Programmed Logic Array). Such circuit implementations entail too wide integrated circuit occupancy.